A kinetics study involving the oxidation of Ce³⁺ to Ce⁴⁺ by ozone, in nitric acid medium, has been reported. Higher concentration of ozone, cerium and nitric acid were observed to be favorable for oxidation. The fractional orders with respect to O₃, Ce³⁺ and H⁺ concentrations were found to be 1.21, 0.68 and 0.54 respectively. Temperature dependence of the rate constant was established, by performing the experiments at five different temperatures ranging from 19 to 62°C. The pre-exponential factor (k_0c) and activation energy (E_ac) came out to be 6.29x10⁶ kmole^-1.43 m^4.29 s^-1 and 43.49 kJ mol^-1 respectively. Kinetics data were also treated to replace species concentrations by activities, giving rise to a new activity based more rigorous rate equation.